Occupancy certificate authorises customers to stay in the property. It is issued by the metropolitan authorities after all other related supporting documents, stating that requirements such as building standards, fire and elevator safety norms, drainage and so on, are in place.
However since the building has been completed and occupied for more than 8 years, you may not get OC from the authorities at this stage.
It may not be necessary to obtain OC at this stage especially when you have already availed home loan from a bank and have even discharged the same.
Since you have already got electricity connections and water supply, the OC may not assume any importance at this stage.
You may sell the property without OC, there wont be any legal impediment in it.